Resolving Metal GPU timers

Published on . Filed under metal programming

Almost a year ago, with macOS 10.15, Apple finally added GPU timer queries to Metal. The documentation for it is incredibly lacklustre to this day, saying the following about [MTLCounterResultTimestamp timestamp]: A timestamp. That's pretty useless, there's no unit attached to it! I ended up writing the following tweet last December when I first implemented GPU timers for Metal: The documentation for MTLCounterResultTimestamp.timestamp says it's "A timestamp." But what unit, Apple? Read post

Debugging VK_ERROR_DEVICE_LOST with Nvidia Device Diagnostics

Published on . Filed under debugging graphics vulkan

If you are working with Vulkan, chances are that at some point you'll run into a VK_ERROR_DEVICE_LOST error. It's the worst kind of error, chances are that your GPU choked on some data sometime about a frame or two ago and the position where you received the error is nowhere near where the GPU actually decided to throw up its hands and give up. This is of course because GPUs and CPUs are inherently decoupled from each other, and when you submit your work from the CPU to the GPU, the GPU will start crunching your numbers while in the meantime the CPU goes on with its busy life doing other things. Read post

Fragment shader based interior mapping

Published on . Filed under programming graphics

Seems like everybody is excited about the fake interior mapping in Spiderman these days. Here is a Kotaku video showing them off: Now, the technique itself is nothing new, it's been proposed by Joost van Dongen who published a paper about it here. The idea is to divide the space into evenly sized “rooms” and then cast a ray in the fragment shader to figure out whether the ceiling/floor or a wall was hit, and then map a texture on top. Read post

Automatic detection of profiling tools

Published on . Filed under programming debugging

Let's say that you occasionally look at your application with NSight, VTune, or any other profiling tool of choice. Naturally you want to add debug markers into your application, but you might not necessarily ship with them or have them run at all when no profiling tool is attached. You could put them behind a command line flag, but I prefer automatic discovery: One build, when run with NSight, having all the debug markers I need to dissect a frame, and when run without NSight not doing any of that overhead. Read post

The curious case of 'ìe°[^]├UëÕ]Ús UëÕâýj'

Published on . Filed under firedrake programming debugging

11 months ago was the last time I touched firedrake, and last weekend the urge to mess with it caught me again. So I set up WSL, installed all necessary dependencies and opened firedrake. I fired up the last compiled version I had, just to remind myself of where I had left things, and I QEMU was happy to dump my debug printf()'s via the virtual UART into stdout. All was good. Read post

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